Display device

ABSTRACT

An optical stacking structure includes a color filter including a plurality of quantum dots which absorbs a first light and emits at least one of second light and third light that are different from the first light, a first optical filter layer disposed on the color filter, and a second optical filter layer disposed on the opposite side of the first optical filter based on the color filter. The first optical filter blocks at least a part of the first light, and the second optical filter transmits at least a part of the first light and reflects at least a part of the second light and the third light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/088,247, filed on Apr. 1, 2016, which claims priority to KoreanPatent Application No. 10-2015-0132246 filed on Sep. 18, 2015, and allthe benefits accruing therefrom under 35 U.S.C. § 119, the content ofwhich in its entirety is herein incorporated by reference.

BACKGROUND 1. Field

The disclosure relates to a display device that displays an image.

2. Description of the Related Art

A display device such as a liquid crystal display (“LCD”), a plasmadisplay device, an organic light emitting diode (“OLED”) display, andthe like are widely used, and in particular, the LCD havingcharacteristics of high visibility, thin thickness, low powerconsumption, low exothermicity, and the like, is widely used for variousdevices such as a mobile device, a computer monitor, a television(“TV”), and the like.

The LCD typically includes two display panels including electricfield-generating electrodes such as a pixel electrode, a commonelectrode and the like, and a liquid crystal layer disposed between thetwo display panels. The LCD displays an image by applying a voltage tothe electric field-generating electrodes, generating an electric fieldin the liquid crystal layer, determining alignment of the liquid crystalmolecules of the liquid crystal layer through the electric field, andcontrolling polarization of incident light.

SUMMARY

An exemplary embodiment provides a display device having improvedphoto-efficiency and viewing angle relative to power consumption.

An exemplary embodiment of a display device includes a light sourcewhich provides a first light, a color filter including a plurality ofquantum dots which absorbs the first light and emits at least one ofsecond light and third light, where the second light and the third lightare different from the first light, a first optical filter layerdisposed on the color filter, where the first optical filter layerblocks at least a part of the first light, and a second optical filterlayer disposed between the light source and the color filter, where thesecond optical filter layer transmits at least a part of the first lightand reflects at least a part of the second light and the third light.

In an exemplary embodiment, the color filter may include a first regionwhich emits the first light, a second region which emits the secondlight, and a third region which emits the third light, and the firstoptical filter layer may be disposed at a region corresponding to thesecond region and the third region.

In an exemplary embodiment, the first light may be a blue light, thesecond light may be a green light, and the third light may be a redlight.

In an exemplary embodiment, the first region may include a transparentbody.

In an exemplary embodiment, the display device may further include afirst substrate and a second substrate disposed opposite to the firstsubstrate, and the first optical filter layer, the color filter and thesecond optical filter layer may be disposed between the first substrateand the second substrate.

In an exemplary embodiment, the first optical filter layer, the colorfilter and the second optical filter layer may be sequentially stackedone on another.

In an exemplary embodiment, the display device may further include aliquid crystal layer disposed between the first substrate and the secondsubstrate, and the first optical filter layer, the color filter and thesecond optical filter layer are disposed on the liquid crystal layer.

In an exemplary embodiment, the quantum dot may include a plurality offirst quantum dots which absorbs the first light and emits the secondlight having a longer wavelength than the first light, and a pluralityof second quantum dots which absorbs the first light and emits the thirdlight having a longer wavelength than the first light and the secondlight.

In an exemplary embodiment, the first quantum dots and the secondquantum dots may have different sizes as each other.

In an exemplary embodiment, the first optical filter layer may transmitlight having a longer wavelength than the first light, and may blocklight having a wavelength of less than or equal to about 500 nanometers(nm).

In an exemplary embodiment, the first optical filter layer may have astacking structure, where the stacking structure includes a first layerhaving a high refractive index and a second layer having a lowrefractive index and disposed on the first layer.

In an exemplary embodiment, the number of layers in the stackingstructure may be equal to or greater than four.

In an exemplary embodiment, the first layer may have a refractive indexin a range of about 1.8 to about 2.6, and the second layer may have arefractive index in a range of about 1.3 to about 1.8.

In an exemplary embodiment, the first layer may include at least oneselected from hafnium oxide, tantalum oxide, titanium oxide, zirconiumoxide, magnesium oxide, cesium oxide, lanthanum oxide, indium oxide,niobium oxide, aluminum oxide, and silicon nitride.

In an exemplary embodiment, the second layer may include a siliconoxide.

In an exemplary embodiment, the first optical filter layer may include athin film including a metal, a conductive oxide or a combinationthereof.

In an exemplary embodiment, the metal may include at least one selectedfrom aluminum, silver, nickel, and chromium, and the conductive oxidemay include at least one selected indium tin oxide, aluminum zinc oxide,gallium zinc oxide, and indium zinc oxide.

In an exemplary embodiment, the second optical filter layer may reflectlight having a wavelength of greater than about 500 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other features of the invention will become apparent andmore readily appreciated from the following detailed description ofembodiments thereof, taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a cross-sectional view showing an exemplary embodiment of adisplay device according to the invention;

FIG. 2 is a graph showing light characteristics of an exemplaryembodiment of a first optical filter layer in the display device of FIG.1;

FIG. 3 is a graph showing light characteristics of an exemplaryembodiment of a second optical filter layer in the display device ofFIG. 1;

FIG. 4 is a cross-sectional view showing a microcavity structure definedcollectively by a color filter in FIG. 1, the first optical filterlayer, and the second optical filter layer, and a microcavity effectgenerated due to the microcavity structure;

FIG. 5 is a cross-sectional view showing first to third regions of thecolor filter of FIG. 4 when the color filter is partitioned into threeregions;

FIG. 6 is a cross-sectional view showing an alternative exemplaryembodiment of the first optical filter layer in the display device ofFIG. 1;

FIG. 7 is a cross-sectional view showing another alternative exemplaryembodiment of the first optical filter layer in the display device ofFIG. 1; and

FIG. 8 is a cross-sectional view showing an exemplary variation of aquantum dot in the display device of FIG. 1.

DETAILED DESCRIPTION

The invention now will be described more fully hereinafter withreference to the accompanying drawings, in which various embodiments areshown. This invention may, however, be embodied in many different forms,and should not be construed as limited to the embodiments set forthherein. Rather, these embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of theinvention to those skilled in the art. Like reference numerals refer tolike elements throughout.

It will be understood that when an element is referred to as being “on”another element, it can be directly on the other element or interveningelements may be present therebetween. In contrast, when an element isreferred to as being “directly on” another element, there are nointervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer or section from another element, component, region, layer orsection. Thus, “a first element,” “component,” “region,” “layer” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother element as illustrated in the Figures. It will be understoodthat relative terms are intended to encompass different orientations ofthe device in addition to the orientation depicted in the Figures. Forexample, if the device in one of the figures is turned over, elementsdescribed as being on the “lower” side of other elements would then beoriented on “upper” sides of the other elements. The exemplary term“lower,” can therefore, encompasses both an orientation of “lower” and“upper,” depending on the particular orientation of the figure.Similarly, if the device in one of the figures is turned over, elementsdescribed as “below” or “beneath” other elements would then be oriented“above” the other elements. The exemplary terms “below” or “beneath”can, therefore, encompass both an orientation of above and below.

“About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

Hereinafter, exemplary embodiments of the invention will be describedwith reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an exemplary embodiment of adisplay device according to the invention.

Referring to FIG. 1, an exemplary embodiment of a display device 100includes a light source 10, a lower panel 11 and an upper panel 12.

The light source 10 provides the lower panel 11 and the upper panel 12with first light. The light source 10 may include a light emitter thatemits the first light. In an exemplary embodiment, the first lightemitted from the light source 10 may be light in a visible light region,e.g., light having relatively higher energy in a visible light region,for example, a blue light. In such an embodiment, the blue light may beprovided to the lower panel 11 and the upper panel 12 as the firstlight.

The light source 10 may include a light emitting region including alight emitter and a light guide that supplies (or guides to supply) theblue light emitted from the light emitting region toward the lower panel11. The light emitting region may be positioned on a side of the lightguide or beneath the light guide.

The lower panel 11 includes a first substrate (SU1) including or formedof glass, plastic and the like, and a wire layer (TA) including a thinfilm transistor and disposed on the first substrate (SU1). The wirelayer (TA) may include a gate line, a sustain voltage line, a gateinsulating layer, a data line, a source electrode, a drain electrode, asemiconductor, a protective layer, and the like. In such an embodiment,the thin film transistor is connected to the gate line and the dataline. In such an embodiment, a pixel electrode (PE) is disposed on thewire layer (TA). The structure of the gate line, the data line, thesource electrode, the drain electrode, the semiconductor and the pixelelectrode may vary in exemplary embodiments.

The gate line and the sustain voltage line are electrically separated ordisconnected from each other, and the data line is insulated from andcrosses the gate line and the sustain voltage line. The gate electrode,the source electrode and the drain electrode respectively define acontrol terminal, an input terminal and an output terminal of the thinfilm transistor. The drain electrode is electrically connected to thepixel electrode (PE).

The pixel electrode (PE) may include or be made of a transparentconductive material of indium tin oxide (“ITO”) or indium zinc oxide(“IZO”), and generate an electric field to control arrangementdirections of liquid crystal molecules.

An alignment layer (AL) is disposed on the pixel electrode (PE). Thealignment layer (AL) may include at least one of polyamic acid,polysiloxane, polyimide, and the like that are generally-used materialsfor a liquid crystal alignment layer. The alignment layer (AL) mayinitially arrange or pretilt liquid crystal molecules in the liquidcrystal layer (LC). Positions of the alignment layer (AL) may bedifferent set in exemplary embodiments. In exemplary embodiments, thealignment layer (AL) may be disposed over or under the liquid crystallayer (LC). In an exemplary embodiment, as shown in FIG. 1, thealignment layer (AL) may be disposed over and under the liquid crystallayer (LC). Alternatively, the alignment layer (AL) may be omitted.

The liquid crystal layer (LC) is disposed between the lower panel 11 andthe upper panel 12. The liquid crystal layer LC may have a thickness ina range of about 5 micrometers (μm) to about 6 μm, for example. Kinds ofliquid crystal molecules in the liquid crystal layer LC, or a drivingmanner of the liquid crystal layer LC, may vary in exemplaryembodiments.

A first polarizer POL1 is disposed on (e.g., adhered to) a rear side (abottom surface or an outer surface) of the first substrate SU1. Thefirst polarizer POL1 may include a polarizing element and a protectivelayer, and the protective layer may include tri-acetyl-cellulose(“TAC”). In an alternative exemplary embodiment, the first polarizerPOL1 may be disposed between the first substrate SU1 and the wire layerTA, or at other positions in the lower panel 11.

A common electrode (CE) is disposed on the liquid crystal layer LC. Thecommon electrode (CE) may include or be made of a transparent conductivematerial, such as ITO or IZO, and may generate an electric field tocontrol arrangement directions of liquid crystal molecules. A positionof the common electrode (CE) may vary in exemplary embodiments. In oneexemplary embodiment, for example, the common electrode (CE) may be onthe lower panel 11.

The upper panel 12 includes a second substrate (SU2) including or formedof transparent glass, plastic, or the like, and a first optical filterlayer 30 disposed on (e.g., below) the second substrate (SU2).

The first optical filter layer 30 may, for example, block light in apart of a visible light wavelength region but pass light in the otherwavelength regions. In one exemplary embodiment, for example, the firstoptical filter layer 30 may block a blue light but pass other lightexcept for the blue light. In one exemplary embodiment, for example, agreen light, a red light and/or a yellow light as a combination thereofmay be transmitted through the first optical filter layer 30.

FIG. 2 is a graph showing light transmittance depending on a wavelengthof a first optical filter layer in the display device of FIG. 1.

Referring to FIG. 2, an exemplary embodiment of the first optical filterlayer 30 may substantially block the blue light, for example, a lighthaving a wavelength less than or equal to about 500 nanometers (nm), andmay transmit remaining visible light, for example, a light having awavelength greater than about 500 nm and less than or equal to about 700nm. In one exemplary embodiment, for example, the remaining visiblelight having a wavelength greater than about 500 nm and less than orequal to 700 nm may have light transmittance of greater than or equal toabout 70%.

In one exemplary embodiment, for example, the color filter 20 of thedisplay device 100 includes a plurality of first regions (PX1) fordisplaying blue, a plurality of second regions (PX2) for displayinggreen, and a plurality of third regions (PX3) for displaying red. Insuch an embodiment, the first optical filter layer 30 may expose (or bedisposed not to overlap) the first region (PX1) for displaying blue anddisposed on or to overlap the second region (PX2) for displaying greenand the third region (PX3) for displaying red. Accordingly,deterioration of display characteristics of the first region (PX1) fordisplaying blue by the first optical filter layer 30 may be effectivelyprevented.

In such an embodiment, the first optical filter layer 30 of the displaydevice 100 works as a band-pass filter (“BPF”) that blocks light in awavelength region corresponding to the blue light but passing light inthe other wavelength regions, for example, corresponding to a greenlight, a yellow light, a red light, and the like other than the bluelight. In such an embodiment, the first optical filter layer 30 may be along-wave pass filter (“LWPF”) that selectively passes a green light, ayellow light, a red light and the like having a relatively longwavelength region, e.g., a visible light having a wavelength longer thanthat of a blue light.

In an exemplary embodiment, the first optical filter layer 30 may be,for example, a semi-transmissive layer.

In one exemplary embodiment, for example, the first optical filter layer30 may have, for example, a distributed Bragg reflection (“DBR”)structure. In such an embodiment, the first optical filter layer 30 mayinclude a plurality of layers having different refractive indices, forexample, alternately stacked layers having different refractive indices.In one exemplary embodiment, for example, a the first optical filterlayer 30 may include first layer 31 having a high refractive index and asecond layer 32 having a low refractive index.

The first layer 31 may have, for example, a refractive index (n1) in arange of about 1.8 to about 2.6, for example, about 1.9 to about 2.6. Inan exemplary embodiment, the first layer 31 may include, for example, atleast one selected from hafnium oxide, tantalum oxide, titanium oxide,zirconium oxide, magnesium oxide, cesium oxide, lanthanum oxide, indiumoxide, niobium oxide, aluminum oxide and silicon nitride. The firstlayer 31 may include at least one of other materials having a refractiveindex in the above-described range in alternative exemplary embodiments.

The second layer 32 may have, for example, a refractive index (n2) in arange of about 1.3 to about 1.8, for example, about 1.4 to about 1.7. Inan exemplary embodiment, the second layer 32 may include, for example, asilicon oxide. The second layer 31 may include at least one of othermaterials having a refractive index in the above-described range inalternative exemplary embodiments.

As the difference between the refractive index (n1) of the first layer31 and the refractive index (n2) of the second layer 32 increases, thefirst optical filter layer 30 may have higher wavelength selectivity.

In an exemplary embodiment, the first layer 31 and the second layer 32may have a thickness and a number of layers determined by the refractiveindex and reflection wavelength of each layer. In one exemplaryembodiment, for example, the first layer 31 may have a thickness in arange of about 3 nm to about 300 nm, and the second layer 32 may have athickness in a range of about 3 nm to about 300 nm. In an exemplaryembodiment, the first optical filter layer 30 may have a total thicknessin a range of about 3 nm to about 10,000 nm. In one exemplaryembodiment, for example, the first optical filter layer 30 may have atotal thickness in a range of about 300 nm to about 10,000 nm, or forexample, about 1000 nm to about 10,000 nm. The first layer 31 may havethe same thickness and material as those of the second layer 32.

In such an embodiment, the first optical filter layer 30 has a stackingstructure and thus may block a blue light but pass a green light, a redlight, and/or a yellow light as a combination thereof except for theblue light out of the visible light.

The blue light blocked from the first optical filter layer 30 may bereflected from the first optical filter layer 30 and thus be opticallyrecycled. The specific composition of the first optical filter layer 30and an optical recycling effect based thereon will be described later indetail.

In an exemplary embodiment, a light blocking member (BM) is disposedbeneath the first optical filter layer 30. The light blocking member(BM) may include or be formed of a material that passes no light, forexample, of a metal particle including chromium (Cr), silver (Ag),molybdenum (Mo), nickel (Ni), titanium (Ti), tantalum (Ta), or the like,an oxide thereof, or a combination thereof. The light blocking member(BM) effectively prevents light leakage of the display device 100 andimproves contrast. Light blocking members (BM) are disposed to be spacedapart from each other by a predetermined distance, and the color filter20 is disposed in a space defined between the light blocking members(BM), as shown in FIG. 1.

In an exemplary embodiment, the color filter 20 includes a quantum dot 2that absorbs light supplied thereto and emits light having otherwavelengths. In an exemplary embodiment, the quantum dot 2 may include afirst quantum dot 2 a that absorbs the first light and emits a secondlight having a longer wavelength than that of the first light, and asecond quantum dot 2 b that absorbs the first light and emits a thirdlight having a longer wavelength than those of the first light and thesecond light.

The shape of the quantum dot 2 is not particularly limited. In oneexemplary embodiment, for example, the quantum dot 2 may have aspherical shape as shown in FIG. 1, may have other shapes of a pyramidalshape or a multi-arm shape, or may be a cubic nanoparticle, a nanotube,a nanowire, a nanofiber, or a particle having a nanosheet-like shape.

The color filter 20 may be partitioned into the first region (PX1) thatdisplays the first light, the second region (PX2) that displays thesecond light, and the third region (PX3) that displays the third light.In an exemplary embodiment, the first region (PX1) may display a bluelight as the first light, the second region (PX2) may display a greenlight as the second light, and the third region (PX3) may display a redlight as the third light.

A blue filter may be disposed in the first region (PX1), and the bluefilter may be a transparent body 20 a that emits the blue light suppliedfrom the light source 10 without changing the wavelength of the bluelight.

In an exemplary embodiment, as shown in FIG. 1, the transparent body 20a fills the first region (PX1) entirely and contacts the secondsubstrate (SU2), but heights, sizes, and the like of the transparentbody 20 a may be variously modified. The transparent body 20 a mayinclude scatter-inducing particles that do not change the wavelength ofthe blue light but that change the moving direction of the blue light.

In an alternative exemplary embodiment, the transparent body 20 a may beomitted. In such an embodiment, a hollow may be defined or formed in thefirst region (PX1).

The second region (PX2) may display a green light, and a green filter 20b that changes the blue light supplied from the light source 10 into agreen light may be disposed therein.

The green filter 20 b includes the first quantum dot 2 a excited byreceiving the blue light and then emitting a green light whilestabilized in a ground state.

The third region (PX3) displays a red light, and a red filter 20 c thatchanges the blue light supplied from the light source 10 into a redlight may be disposed therein.

The red filter 20 c includes a second quantum dot 2 b excited byreceiving the blue light and then emitting red light while stabilized ina ground state.

In an exemplary embodiment, where the blue light supplied from the lightsource 10 is scattered by scatter-inducing particles in the firstquantum dot 2 a, the second quantum dot 2 b and the transparent layer 20a, and is then externally emitted and displays an image, the emittedlight may move in a wide direction and have no grayscale changedepending on a position, and accordingly, the display device 100 mayhave a wide viewing angle.

In an exemplary embodiment, the green filter 20 b and the red filter 20c respectively including the quantum dot 2 may be formed by coating aphotosensitive composition including a binder, a photopolymerizablemonomer, a photoinitiator, and a solvent other than the quantum dot oneach of the second region (PX2) and the third region (PX3).

In such an embodiment, the first quantum dot 2 a and the second quantumdot 2 b may include or be formed of the same material but have differentsizes, so that incident blue light may be respectively emitted as agreen light and a red light having different wavelengths.

In one exemplary embodiment, for example, the first quantum dot 2 a mayhave a smaller size than the second quantum dot 2 b and thus emit agreen light (G) having a middle wavelength of about 530±5 nm and a fullwidth at half maximum (“FWHM”) from about 40 nm to about 60 nm, that is,relatively high energy. In such an embodiment, the second quantum dot 2b has a larger size than that of the first quantum dot 2 a and thus mayemit a red light (R) having a wavelength of about 625±5 nm and a FWHMfrom about 40 nm to about 60 nm, that is, relatively low energy.

The quantum dot is not particularly limited, but may be a known orcommercially available quantum dot. In one exemplary embodiment, forexample, the quantum dot may include a Group II-VI compound, a GroupIII-V compound, a Group IV-VI compound, a Group IV compound, or acombination thereof.

The Group II-VI compound may be at least one selected from a binaryelement compound including CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe,HgTe, MgSe, MgS, and a mixture thereof; a ternary element compoundincluding CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe,HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe,HgZnTe, MgZnSe, MgZnS, and a mixture thereof; and a quaternary elementcompound including HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS,CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and a mixture thereof.

The Group III-V compound semiconductor may be at least one selected froma binary element including GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb,InN, InP, InAs, InSb, and a mixture thereof; a ternary element compoundincluding m GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs,AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, and a mixture thereof; and aquaternary element compound including GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs,GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs,InAlNSb, InAlPAs, InAlPSb, and a mixture thereof. The Group IV-VIcompound may be at least one selected from a binary element compoundincluding SnS, SnSe, SnTe, PbS, PbSe, PbTe, and a mixture thereof; aternary element compound including SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe,PbSTe, SnPbS, SnPbSe, SnPbTe, and a mixture thereof; and a quaternaryelement compound including SnPbSSe, SnPbSeTe, SnPbSTe, and a mixturethereof.

The Group IV compound may be selected from a singular element compoundincluding Si, Ge, and a mixture thereof; and a binary element compoundincluding SiC, SiGe, and a mixture thereof.

In such an embodiment, the binary element compound, the ternary elementcompound, or the quaternary element compound may be present with auniform concentration in a particle, or may be present with a locallydifferent concentration in a single particle. The quantum dot 2 may havea core-shell structure, in which a quantum dot 2 surrounds another(different) quantum dot 2. The interface of the core and the shell mayhave a concentration gradient such that the concentration of theelement(s) of the shell decreases toward the core. The quantum dot mayhave a single core of a quantum dot and multi-shells surrounding thecore. The multi-layered shell structure has at least two shells, each ofwhich may be a single composition, an alloy, or have a concentrationgradient.

In an exemplary embodiment, the materials of the shell of the quantumdot may have a higher energy bandgap than that of the core, and therebythe quantum dot may exhibit a quantum confinement effect moreeffectively. In an exemplary embodiment, where the quantum dot 2 is amulti-shell type of quantum dot particle, the bandgap of the material ofan outer shell may be higher energy than that of the material of aninner shell (a shell that is closer to the core). In such an embodiment,the quantum dot may emit light of a wavelength ranging from ultraviolet(UV) to infrared light.

The quantum dot may have quantum efficiency greater than or equal toabout 10%, for example, greater than or equal to about 30%, greater thanor equal to about 50%, greater than or equal to about 60%, greater thanor equal to about 70%, or greater than or equal to about 90%.

In an exemplary embodiment, a second optical filter layer 40 is disposedon a side of the color filter 20. The second optical filter layer 40 maybe disposed to cover overran entire surface of the upper panel 12.

In one exemplary embodiment, for example, the second optical filterlayer 40 may include a plurality of layers having different refractiveindices. In one exemplary embodiment, for example, the second opticalfilter layer 40 may include alternately stacked layers having differentrefractive indices. In such an embodiment, one layer of the plurality oflayers includes a material having a high refractive index and anotherlayer of the plurality of layers includes a material having a lowrefractive index.

In an exemplary embodiment, a layer having a high refractive index ofthe second optical filter layer 40 may include, for example, at leastone selected from hafnium oxide, tantalum oxide, titanium oxide,zirconium oxide, magnesium oxide, cesium oxide, lanthanum oxide, indiumoxide, niobium oxide, aluminum oxide and silicon nitride, but not beinglimited thereto. Alternatively, the layer having a high refractive indexof the second optical filter layer 40 may include various othermaterials having higher refractive indices that the layer having a lowrefractive index according to embodiments.

In an exemplary embodiment, a layer having a low refractive index of thesecond optical filter layer 40 may, for example, include a siliconoxide, but not being limited thereto. Alternatively layer having a lowrefractive index of the second optical filter layer 40 may includevarious other materials having a lower refractive index than a layerhaving a high refractive index.

In such an embodiment, as the difference between the refractive indicesof the layer having a high refractive index and the layer having a lowrefractive index increases, the second optical filter layer 40 may havehigher wavelength selectivity.

In an exemplary embodiment, a thickness and a number of layers of thelayer having a high refractive index and the layer having a lowrefractive index may be determined by the refractive index andreflection wavelength of each layer. In one exemplary embodiment, forexample, the layer having a high refractive index may have a thicknessin a range of about 3 nm to about 300 nm, and the layer having a lowrefractive index may have a thickness in a range of about 3 nm to about300 nm. The second optical filter layer 40 may have a total thickness,for example, in a range of about 3 nm to about 10,000 nm, in a range ofabout 300 nm to about 10,000 nm, or in a range of about 1000 nm to about10,000 nm. In the second optical filter layer 40, the layer having ahigh refractive index and the layer having a low refractive index mayhave the same or different thicknesses, and may include or be formed ofthe same or different materials.

In an exemplary embodiment, the second optical filter layer 40 may passa blue light in a wavelength region less than or equal to about 500 nmbut reflect light in a wavelength region greater than about 500 nm, thatis, a green light, a yellow light, a red light and the like. The secondoptical filter layer 40 may have a reflectance greater than or equal toabout 60%, for example, greater than or equal to about 80%, of light inthe wavelength region of greater than about 500 nm.

FIG. 3 is a graph showing light characteristics of an exemplaryembodiment of a second optical filter layer in the display device ofFIG. 1.

Referring to FIG. 3, an exemplary embodiment of the second opticalfilter layer 40 may substantially transmit a blue light, for example,light having a wavelength less than or equal to about 500 nm, and mayreflect remaining visible light, for example, light having a wavelengthgreater than about 500 nm and less than or equal to 700 nm. In oneexemplary embodiment, for example, the second optical filter layer 40may have a light transmittance greater than or equal to about 70% withrespect to the blue light having a wavelength less than or equal to 500nm.

In an exemplary embodiment, the second optical filter layer 40 mayfunction as a BPF that selectively passes a wavelength regioncorresponding to a blue light. In such an embodiment, the second opticalfilter layer 40 blocks a wavelength region outside the blue light, forexample, a wavelength region corresponding to a green light, a yellowlight, a red light, and the like, and thus may function as a short-wavepass filter (“SWPF”).

Accordingly, the green light, the yellow light, the red light and thelike may not pass the second optical filter layer 40 but may bereflected toward the first optical filter layer 30 and thus be opticallyrecycled.

FIG. 1 shows an exemplary embodiment having a stacking structure inwhich the first optical filter layer 30, the color filter layer 20 andthe second optical filter layer 40 are sequentially stacked from thetop. In such an embodiment, the stacking structure may be positioned inthe upper panel 12, but not being limited thereto. Alternatively, thestacking structure may be variously positioned between the firstsubstrate (SU1) and the second substrate (SU2) depending on a method ofdriving a display device, an environment for using the device, and thelike.

In one exemplary embodiment, for example, the stacking structure may bepositioned between the liquid crystal layer (LC) and the first substrate(SU1). In such an embodiment, the lower panel 11 includes the stackingstructure, and may distinguish the first light supplied from the lightsource 10 into first light, second light and third light.

In an exemplary embodiment, the stacking structure may function as atype of optical resonator due to the first optical filter layer 30 andthe second optical filter layer 40. In such an embodiment, lightrespectively reflected from the first optical filter layer 30 and thesecond optical filter layer 40 may be repeatedly reflected between thefirst optical filter layer 30 and the second optical filter layer 40 andresonated. In such an embodiment, light reinforced and interfered withthrough the resonance may finally pass the first optical filter layer30.

Accordingly, such a stacking structure will hereinafter be referred toas a microcavity structure.

In an exemplary embodiment, a second polarizer (POL2) is disposed on(e.g., adhered under) the second optical filter layer 40. The secondpolarizer (POL2) may include a polarizing element and a protectivelayer, and the protective layer may include TAC. An insulation layer(not shown) may be disposed between the second polarizer (POL2) and thecommon electrode (CE), and electrically insulates the second polarizerPOL2 from the common electrode (CE). In an exemplary embodiment, thesecond polarizer (POL2) may be disposed below (e.g., on an inner surfaceof) the second optical filter layer 40 but not being limited thereto. Inan alternative exemplary embodiment, the second polarizer (POL2) may bedisposed in the upper panel 12, for example, on top of or beneath thecolor filter 20, or may be omitted.

Hereinafter, referring to FIG. 4, the principle and effect of themicrocavity structure defined based on the first optical filter layer 30and the second optical filter layer 40 will be described.

FIG. 4 is a cross-sectional view showing the microcavity structuredefined collectively by the color filter, the first optical filterlayer, and the second optical filter layer in FIG. 1, and a microcavityeffect due to the microcavity structure.

FIG. 4 schematically shows the color filter 20 without partitioning thefirst region (PX1) to the third region (PX3) to illustrate themicrocavity structure and an effect thereof, in an exemplary embodimentwhere a plurality of quantum dots 2 including the first quantum dot 2 aand the second quantum dot 2 b having different sizes are included inthe color filter 20.

Referring to FIG. 4, the first optical filter layer 30, the color filter20 and the second optical filter layer 40 are sequentially disposed, andthe light source 10 that emits the blue light (B) is disposed below thesecond optical filter layer 40.

In such an embodiment, the plurality of quantum dots 2 of the colorfilter 20 is excited by the blue light (B) supplied from the lightsource 10 through the second optical filter layer 40, and then emitlight having a particular wavelength while stabilized in a ground state.In such an embodiment, each quantum dot 2 has a discontinuous energybandgap due to a quantum confinement effect, and thus the display device100 may display an image having high color purity.

In such an embodiment, the quantum dot 2 has anisotropic opticalradiation characteristics. Accordingly, the quantum dot 2 may radiatelight in various directions as shown in FIG. 4. In such an embodiment,since light emitted from the quantum dot 2 is radiated not in aparticular direction but in a random direction, photo-efficiency may bedeteriorated. In an exemplary embodiment, the display device 100 mayhave a microcavity structure that amplifies and resonates light emittedfrom the quantum dot 2 and thus emits the resonated light, therebyimproving photo-efficiency.

The microcavity structure amplifies and emits light having a particularwavelength by repeatedly reflecting light between a reflection layer anda semi-reflection layer spaced apart from each other with a distancedetermined based on an optical length, and is called a Fabry-Perotinterferometer or a Fabry-Perot resonator, and such light-amplifyingeffect is called a microcavity effect or a Fabry-Perot multi-beameffect. In an exemplary embodiment, the first optical filter layer 30may function as a semi-transmission layer, and the second optical filterlayer 40 may function as a reflection layer.

In an exemplary embodiment, assuming that the blue light incident intothe color filter 20 is absorbed therein at a zero rate, that lightemitted from the inside of the color filter 20 is a plane wave havinghigh coherence, and that light radiated through the quantum dot 2 hasthe same magnitude, the incident light is multi-reflected on theinterface of the first optical filter layer 30 and the color filter 20and on the interface of the second optical filter layer 40 and the colorfilter 20, and emitted out of the microcavity structure due to themicrocavity effect thereof.

In an exemplary embodiment, the first quantum dot 2 a is excited whenthe blue light (B) enters the first quantum dot 2 a, and then emits thegreen light in a radiation direction while stabilized in a ground state.In such an embodiment, as shown in FIG. 4, when the green light isemitted from the first quantum dot 2 a, a part of the radiated greenlight may directly pass through the first optical filter layer 30, butthe rest of the light is reflected on the surface of the second opticalfilter layer 40, the optical length thereof is changed, and accordingly,the reflected light heads toward the first optical filter layer 30 orcollides with other first quantum dots 2 a and other second quantum dots2 b inside the color filter 20 and is thus reflected and refracted.

The first optical filter layer 30 may emit light around a wavelengthcorresponding to a resonance wavelength of microcavity, for example, aphase of 2τrn (n is an integer), but may re-reflect light at otherphases toward the second optical filter layer 40 when other green lightportions except directly-passing green light (G) reach the first opticalfilter layer 30. The re-reflected light goes back and forth between thefirst optical filter layer 30 and the second optical filter layer 40until the light has a phase of 2τn when the light reaches the firstoptical filter layer 30 and is finally emitted as amplified green light(G′). In such an embodiment, as shown in FIG. 4, the amplified greenlight (G′) amplified through reinforcement and interference due to themicrocavity effect is emitted along with the directly-passing greenlight (G) and thus may improve photo-efficiency of the green light.

As for a red light, the amplified red light (R′) amplified throughreinforcement and interference due to the microcavity effect is emittedalong with directly-passed red light (R) and thus may improvephoto-efficiency of the red light.

In an exemplary embodiment, the amplified green light (G′) and the redlight (R′) may be amplified based on a Fabry-Perot multi-beaminterference, a dual-beam interference or a combination thereof. In suchan embodiment, multi-light or dual light may be amplified throughreinforcement and interference and emitted as one light, or themulti-beam or dual beam interference may simultaneously occur and leadto amplification.

In such an embodiment, since portions of a green light and a red lightconventionally considered as an optical loss due to anisotropic opticalradiation characteristics by the quantum dot 2 may be reflected andamplified and then emitted as shown in FIG. 4, the green light and thered light may be optically recycled due to the microcavity structure.

In such an embodiment, the blue light not entering the quantum dot 2 butgoing straight toward the first optical filter layer 30 is reflected onthe surface of the first optical filter layer 30. A part of thereflected blue light (B′) may enter the first quantum dot 2 a or thesecond quantum dot 2 b when reflected back to the second optical filterlayer 40. Accordingly, a part of the blue light (B′) reflected by thefirst optical filter layer 30 passes the second optical filter layer 40again and may not go back to the light source 10 but excites the quantumdot 2 and thus optically recycles the blue light.

Hereinafter, referring to FIG. 5, the microcavity effect through thefirst optical filter layer 30 and the second optical filter layer 40will be described in detail by partitioning the color filter 20 intoregions.

FIG. 5 is a cross-sectional view specifically showing first to thirdregions of the color filter of FIG. 4.

Referring to FIG. 5, in an exemplary embodiment, the color filter 20 ofthe display device 100 is partitioned into the first region (PX1) fordisplaying blue light, the second region (PX2) for displaying greenlight, and the third region (PX3) for displaying a red light, unlike theschematic structure of FIG. 4, and the first to third color filters aredisposed in a region corresponding thereto.

The first region (PX1) of the color filter 20 has no microcavity effect,since only the second optical filter layer 40 that functions as areflection layer is provided, and the first optical filter layer 30 thatfunctions as a semi-transmission layer is not provided. Accordingly, ablue may be displayed in the first region (PX1), since blue lightsupplied from the light source 10 is not resonated but passes throughthe transparent blue filter 20 a.

In such an embodiment, the second region (PX2) and the third region(PX3) may each have a microcavity structure formed by the first opticalfilter layer 30 that functions as a semi-transmission layer and thesecond optical filter layer 40 that functions as a reflection layer. Asshown in FIG. 5, the green light and the red light respectively resonateinside the green filter 20 b and the red filter 20 c.

The second region (PX2) may display a green color through the greenlight (G) and the amplified green light (G′) amplified throughresonance, and the third region (PX3) may display a red color throughthe red light (R) and red light (R′) amplified through resonance.

The green and red displayed by the display device 100 are obtained byadding each green and red directly emitted from the quantum dot 2 asdescribed above (spontaneous emission), each amplified green andamplified red, which are amplified through reinforcement andinterference of multi-emitted light due to a microcavity structure(Fabry-Perot multi-beam interference), and each green and red that areamplified through reinforcement and interference of duel emitted lightdue to the microcavity structure (duel beam interference). Accordingly,in such an embodiment, the display device 100 may have about 80% toabout 300%, for example, about 170% to about 300%, or for example, about170% to about 250% improved photo-efficiency when compared with aconventional display device having no microcavity structure.

The green and red displayed by the display device 100 relate to anoptical length, and thus spectral radiance of the green light and thered light finally passing through a microcavity structure may be changedby adjusting a distance between a reflection layer and asemi-transmission layer including the microcavity structure.

In one exemplary embodiment, for example, as shown in FIG. 5, the greenfilter 20 b and the red filter 20 c may have the same thickness ordifferent thicknesses determined based on an optimal resonant distancecorresponding to each wavelength, and the optimal resonant distancecorresponding to each wavelength between the first optical filter layer30 and the color filter 20 or between the second optical filter layer 40and the color filter 20 may be reinforced by forming each resonantreinforcement layer having various thicknesses.

In an exemplary embodiment, the color filter 20 is partitioned into eachregion by a light blocking member (BM), and thus may block lightresonating between the first optical filter layer 30 and the secondoptical filter layer 40 from intrusion into the other regions andprevent a color mixture of red, green, and blue from being displayed bythe display device 100.

In such an embodiment, the first optical filter layer 30 that blocksblue light is disposed in the second region (PX2) and the third region(PX3), and may effectively prevent a color mixture of the blue lightwith green and red. In such an embodiment, the display device 100 mayhave an improved color gamut with respect to green and red colors.

In an exemplary embodiment, where the display device 100 includes thequantum dot 2 in the color filter 20 and displays an image when lightsupplied from the light source 10 is scattered by the quantum dot 2 andemitted outside, as described above, the light may be emitted in a widedirection and have no grayscale change depending on a position.Accordingly, in such an embodiment, the display device 100 may have awide viewing angle.

In an exemplary embodiment, the display device 100 may have improvedphoto-efficiency through a microcavity structure by disposing the firstoptical filter layer 30 and the second optical filter layer 40 with thecolor filter 20 in the middle to form the microcavity structure, evenwhen the color filter 20 includes the quantum dot 2 having anisotropicoptical radiation characteristics. In such an embodiment, the displaydevice 100 may have improved photo-efficiency relative to powerconsumption.

Hereinafter, referring to FIGS. 6 to 8, various alternative exemplaryembodiments of the display device 100 will be described. Hereinafter,any repetitive detailed description of the same constituents of thealternative exemplary embodiments as in the display device 100 of FIG. 1will be omitted.

FIG. 6 is a cross-sectional view showing an alternative exemplaryembodiment of a first optical filter layer in the display device of FIG.1.

Referring to FIG. 6, a first optical filter layer 30′ may have astacking structure in which a first layer 31 having a high refractiveindex and a second layer 32 having a low refractive index arealternately stacked one on another such that the stacking structure mayhave up to about 10 layers but at least about 4 layers, for example,about 5 layers.

FIG. 7 is a cross-sectional view showing another alternative exemplaryembodiment of the first optical filter layer in the display device ofFIG. 1.

Referring to FIG. 7, the first optical filter layer 30″ may have, forexample, a half mirror structure. In one exemplary embodiment, forexample, the first optical filter layer 30″ may have a structureincluding a thin film 34 disposed on a substrate 33.

The substrate 33 may include at least one selected from a silicon oxide,an acryl, a polycarbonate, polyethylene terephthalate, polyethylenenaphthalate, and glass. Alternatively, the substrate 33 may include orbe made of other various transparent materials.

The thin film 34 may be disposed on a surface or both of opposingsurfaces of the substrate 33. This thin film 34 has a mirror effect, andthus may selectively pass a part of reinforced and interfered light outof light reaching the first optical filter layer 30″ and reflect theremaining part of light.

The thin film 34 on the surface of the substrate 33 may include a metal,a conductive oxide or a combination thereof. The metal may include atleast one selected from aluminum (Al), silver (Ag), nickel (Ni), andchromium (Cr), and the conductive oxide may include at least oneselected from indium tin oxide, aluminum zinc oxide, potassium zincoxide, and indium zinc oxide.

However, the thickness and material of the substrate 33 and the thinfilm 34, the density of the thin film 34, and the like may variouslymodified in a way, such that a first optical filter layer 30″ blocks awavelength of less than or equal to about 500 nm corresponding to a bluelight but passes a wavelength of greater than about 500 nm, as shown inFIG. 2.

FIG. 8 is a cross-sectional view showing another alternative exemplaryembodiment of the first optical filter layer, in which the first quantumdot and the second quantum dot have the same size in FIG. 1.

In an exemplary embodiment, as shown in FIG. 8, a first quantum dot 2 a′and a second quantum dot 2 b′ may have the same size as each other. Insuch an embodiment, the color filter 20 includes a plurality of quantumdots 2′ having the same size. Herein, the first quantum dot 2 a′ and thesecond quantum dot 2 b′ may include or be formed of different materialsin the second region (PX2) and the third region (PX3).

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. An optical stacking structure comprising: a colorfilter comprising a plurality of quantum dots which absorbs first lightand emits at least one of second light and third light, wherein thesecond light and the third light are different from the first light; afirst optical filter layer disposed on the color filter, wherein thefirst optical filter blocks at least a part of the first light; and asecond optical filter layer disposed on the opposite side of the firstoptical filter based on the color filter, wherein the second opticalfilter transmits at least a part of the first light and reflects atleast a part of the second light and the third light, wherein the firstoptical filter layer, the color filter and the second optical filterlayer are sequentially stacked one on another, the first optical filterlayer functions as a semi-transmission layer so that the first opticalfilter layer emits light around a wavelength corresponding to aresonance wavelength of a microcavity structure defined collectively bythe first optical filter layer, the color filter and the second opticalfilter layer, and the second optical filter layer functions as areflection layer so that light, except for the light around thewavelength corresponding to the resonance wavelength of the microcavitystructure, goes back and forth between the first optical filter layerand the second optical filter layer.
 2. The optical stacking structureof claim 1, wherein the color filter comprises: a first region whichemits the first light; a second region which emits the second light; anda third region which emits the third light, wherein the first opticalfilter layer is disposed at a region corresponding to the second regionand the third region.
 3. The optical stacking structure of claim 2,wherein the first region comprises a transparent body.
 4. The opticalstacking structure of claim 2, wherein the second optical filter layeris disposed at a region corresponding to the first region, the secondregion, and the third region.
 5. The optical stacking structure of claim1, further comprising: a first substrate; and a second substratedisposed opposite to the first substrate, wherein the first opticalfilter layer, the color filter and the second optical filter layer aredisposed between the first substrate and the second substrate.
 6. Theoptical stacking structure of claim 1, wherein the quantum dotscomprise: a plurality of first quantum dots which absorbs the firstlight and emits the second light having a longer wavelength than thefirst light; and a plurality of second quantum dots which absorbs thefirst light and emits the third light having a longer wavelength thanthe first light and the second light.
 7. The optical stacking structureof claim 6, wherein the first quantum dots and the second quantum dotshave different sizes from each other.
 8. The optical stacking structureof claim 1, wherein the first optical filter layer transmits lighthaving a longer wavelength than the first light.
 9. The optical stackingstructure of claim 1, wherein the first optical filter layer blockslight having a wavelength less than or equal to about 500 nanometers.10. The optical stacking structure of claim 1, wherein the first lightis a blue light, the second light is a green light, and the third lightis a red light.
 11. The optical stacking structure of claim 1, whereinthe first optical filter layer has a multi-layered structure, and themulti-layered structure comprises: a first layer having a highrefractive index; and a second layer having a low refractive index anddisposed on the first layer.
 12. The optical stacking structure of claim11, wherein the number of the layers in the multi-layered structure isequal to or greater than four.
 13. The optical stacking structure ofclaim 11, wherein the first layer has a refractive index in a range ofabout 1.8 to about 2.6.
 14. The optical stacking structure of claim 11,wherein the second layer has a refractive index in a range of about 1.3to about 1.8.
 15. The optical stacking structure of claim 11, whereinthe first layer comprises at least one selected from hafnium oxide,tantalum oxide, titanium oxide, zirconium oxide, magnesium oxide, cesiumoxide, lanthanum oxide, indium oxide, niobium oxide, aluminum oxide, andsilicon nitride.
 16. The optical stacking structure of claim 11, whereinthe second layer comprises a silicon oxide.
 17. The optical stackingstructure of claim 1, wherein the first optical filter layer comprises:a film comprising at least one selected from a metal, a conductive oxideand a combination thereof.
 18. The optical stacking structure of claim16, wherein the metal comprises at least one selected from aluminumsilver, nickel, and chromium, and the conductive oxide comprises atleast one selected from indium tin oxide, aluminum zinc oxide, galliumzinc oxide and indium zinc oxide.
 19. The optical stacking structure ofclaim 1, wherein the second optical filter layer has a reflectancegreater than or equal to about 60% to light having a wavelength greaterthan about 500 nanometers.
 20. The optical stacking structure of claim1, wherein the second optical filter layer has a light transmittancegreater than or equal to about 70% to light having a wavelength greaterthan about 500 nanometers.
 21. The optical stacking structure of claim1, wherein the first optical filter has a light transmittance greaterthan or equal to about 70% to light having a wavelength greater thanabout 500 nanometers and less than or equal to 700 nanometers.
 22. Theoptical stacking structure of claim 11, wherein the first optical filterhas a light transmittance greater than or equal to about 70% to lighthaving a wavelength greater than about 500 nanometers and less than orequal to 700 nanometers.
 23. The optical stacking structure of claim 1,wherein the first optical filter layer and the second optical filterlayer are spaced apart from each other with a distance determined basedon an optical length.